[Seaside] monticello remote repositories

[Stephen Pair]

For the ObjectStudio team edition, I implemented a 3-way merge tool, and
I can say from experience that having such a tool is quite nice.  A
3-way merge in Smalltalk isn't quite as critical as in other file based
languages, but it is useful.

In the example that Julian gives below, a three way tool takes the guess
work out of the merge.  Also, showing the diffs between a version and a
base version is much more meaningful than showing the diffs between to
diverging versions because it shows the exact changes that were made by
a developer; which makes it much easier to see what those changes as
whole were intended to accomplish.

- Stephen

> -----Original Message-----
> From: seaside-admin@lists.squeakfoundation.org 
> [mailto:seaside-admin@lists.squeakfoundation.org] On Behalf 
> Of Julian Fitzell
> Sent: Sunday, December 29, 2002 9:40 PM
> To: seaside@lists.squeakfoundation.org
> Subject: Re: [Seaside] monticello remote repositories
> 
> 
> Andreas,
> 
> I agree that 3-way merging is probably less useful in Squeak than in 
> other languages since methods do often end up being very 
> short.  I'm not 
> convinced though, that you couldn't to 3-way merge at a finer 
> granularity than line-by-line.  I think by analyzing the 
> parsed method 
> you ought to be able to tell, for example that if you had:
> 
> foo
>    ^ self bar
> 
> And the two modified versions:
> 
> foo
>    ^ self bar asString
> 
> and
> 
> foo
>    ^ someBool ifTrue: [self bar] ifFalse: [self baz]
> 
> You might well be able to merge both of these changes into:
> 
> foo
>    ^ someBool ifTrue: [self bar asString] ifFalse: [self baz]
> 
> 
> I haven't given this too much thought, nor have I even looked in much 
> detail at the parsed structure of the method, so I way well be 
> completely wrong.  But it's still an interesting idea! :)
> 
> But I certainly concede that having automated 3-way merge is 
> by no means 
> a necessity and probably of less need in Squeak code than in 
> C code for 
> example.
> 
> I still don't quite see how a diff between my modified 
> version and the 
> version on the server is helpful, though.  It seems to me 
> that that diff 
> would contain both the changes made between the two 
> repository versions 
> and the *reverse* (ie removal) of the changes made in your local copy.
> 
> This is where I was wondering if I was misunderstanding you or if I'm 
> just not seeing the benefit.  I certianly think that long before 
> automated merging is done, being able to see all 3 versions and their 
> respective diffs would be useful.
> 
> Julian
> 
> Andreas Raab wrote:
> > Julian,
> > 
> > I think that three way merging/diffing is probably overrated in the 
> > praxis of Squeak (or any other Smalltalk) coding. Three way 
> > merges/diffs are mostly needed if the granularity of the 
> code you are 
> > looking at is very large (e.g., at the file level or at very long 
> > method level). For most portions of code I have ever looked at in 
> > Squeak (and believe me it's been lots ;-) I have hardly ever needed 
> > the three-way comparison. Mostly because if you see a diff against 
> > *your* code (e.g., code that you have modified) and use the source 
> > code manager in a reasonable way (by which I mean to update 
> every now 
> > and then and not every other year) you can usually remember 
> what the 
> > point of a particular change was and see if that update 
> addresses the 
> > problem or obsoletes it or relates to it at all. From my personal 
> > experiences that's mostly what you need.
> > 
> > Most cases I remember where I wanted three way diffs were 
> exactly what 
> > I described above - either "large methods" (like Interpreter
> > class>>initializePrimitiveTable) or places where I wanted to compare
> > changes on a "file level" (e.g., seeing all the changes 
> being done in 
> > a particular class). Yet, I would still argue that these 
> fall into the 
> > 5% category ;-)
> > 
> > So I'm not claiming that you never need a three way 
> merge/comparison. 
> > But I think you could cover lots and lots of grounds by just using 
> > what's already there.
> > 
> > Cheers,
> >   - Andreas
> 
> 
> 
> -- 
> julian@beta4.com
> Beta4 Productions (http://www.beta4.com)
> 
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